Method and arrangement for handling sheet goods

ABSTRACT

First and second electrodes are spaced apart from each other to define an air gap. A flow of ionic current is established across the air gap from one to the other of the electrodes. Sheet goods are transported along a predetermined path passing through the air gap but without physically contacting the first and second electrodes. The magnitude of the ionic current is monitored in order to determine whether or not an article of sheet goods is located in the air gap.

United 3 States Patent [191 Hartwig et al.

[ METHOD AND ARRANGEMENT FOR HANDLING SHEET GOODS [75] Inventors: Karl Hartwig, Unterhaching;

Giinther Maurischat, Munich, both of Germany Agfa-Gevaert Aktiengesellschaft, Leverkusen, Germany [22] Filed: Aug. 29, 1973 [21] Appl. No.: 392,808

[73] Assignee:

[30] Foreign Application Priority Data Aug. 31, 1972 Germany 2242948 [52] US. Cl. 340/259, 340/282 [51] Int. Cl. G08b 21/00 [58] Field of Search 340/259, 265, 282

[56] References Cited UNITED STATES PATENTS 3,339,125 8/1967 Almy 340/282 X [451 Feb. 25, 1975 3,439,263 4/1969 Broyles 340/265 X 3,609,737 9/1971 Lustig et a1. 3,623,058 11/1971 Maloney 340/259 Primary Examiner-David L. Trafton Attorney, Agent, or Firm-Michael S. Striker [57] ABSTRACT First and second electrodes are spaced apart from each other to define an air gap. A flow of ionic current is established across the air gap from one to the other of the electrodes. Sheet goods are transported along a predetermined path passing through the air gap but without physically contacting the first and second electrodes. The magnitude of the ionic current is monitored in order to determine whether or not an article of sheet goods is located in the air gap.

10 Claims, 1 Drawing Figure MOTOR SHUTOFF ALARM sw/TEH PATENTED P5525975 3.868566 MOTOR SHUTOFF. ALA/2M SWIT'H 1 v I METHOD AND ARRANGEMENT FOR HANDLING SHEET GOODS BACKGROUND OF THE INVENTION The invention relates to methods for detecting improperly transported and/or improperly oriented sheet goods in arrangements for transporting and processing sheet goods, in particular in electrostatic copying arrangements, and furthermore relates to arrangements for accomplishing such detection.

It is already known to detect the moment of travel of the leading or trailing end of a sheet past a predetermined point along a sheet transport path, and also to detect the presence or absence of sheet goods material at a predetermined point along a sheet transport path, through the use of contact-free sensors employed in order to prevent damage to such sheet goods. The sensors are operatively associated with switch arrangements or other controlarrangements for controlling the operation of the sheet transporting of processing machine in dependence upon the detection of properly and improperly transported and/or oriented sheets. It is also known to operatively associate such sensors with alarm arrangements which are automatically activated to give warning of the presence of an improperly transported and/or oriented sheet.

Use of such detection arrangements prevents the sheet transporting and sheet processing arrangements from becoming damaged by improperly transported or improperly oriented sheets, e.g., by a plurality of sheets improperly sticking together and travelling as a single sheet of multiple thickness, or by skew sheets. Such detection arrangements can also be used to initiate a sheet-transport or sheet-handling operation upon detection of the leading edge of a sheet and to terminate such operation upon detection of the trailing edge of a sheet.

Most of the prior-art arrangements for this purpose have operated upon photoelectric principles, and have made us of one or more photocells oriented to respond to light reflected from a detected sheet or oriented to respond. to the blocking of a light source by a sheet. These prior-art arrangements were relatively complicated and subject to malfunction. Numerous difficulties arose as a result of the varying transparency and color of the sheets to be detected, and furthermore as a result of variations in temperature, as a result of exposure of the photocells to stray light, as a result of dirtying of the photocell, as a result of aging of the light sources, and as a result of improper relative orientations between the various components of the system.

SUMMARY OF THE INVENTION It is the general object of the present invention to provide a method and arrangement for the contact-free detection of sheet goods, including streams of spaced sheets, streams of lapped sheets, streams of sheets of single thickness, streams of sheets of multiple thickness such as book or newspaper components, as well as endless webs of sheet material.

More particularly it is the general object of the invention to provide such a method and arrangement which avoid to a very considerable degree the abovediscussed disadvantages of the prior art sheet detection techniques.

These objects, and others which will become more understandable from the following description of a preferred embodiment, can be met, according to one advantageous concept of the invention, by positioning first and second electrode means spaced from each other to define an air gap, and establishing a flow of ionic current across the air gap from one to the other of the electrode means. Sheet goods are transported along a predetermined path passing through the air gap and so oriented that sheet goods travelling through the air gap do not contact the first and second electrode means. The magnitude of the ionic current is monitored in order to determine whether or not an article of sheet goods is located in the air gap. The transporting of the sheet goods and/or the operation of sheet processing machines can be controlled in dependence upon the monitored magnitude of the ionic current.

The method and arrangement according to the invention are advantageous in that they may be employed more or less without regard to variations in sheet transparency and color, and are not detrimentally affected to any great extent by dirtying of the detecting equip ment, aging or small imprecisions in the relative positioning of the different components of the arrangement.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS The single FIGURE depicts in schematic form one exemplary embodiment according to the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The FIGURE depicts in very schematic form only as much of a sheet transporting arrangement and sheet handling machine as is necessary for an understanding of the invention.

Reference numeral 1 designates a source of high voltage, which may be either AC. or DC In the illustrated embodiment the source 1 furnishes at its output a DC.

voltage of +5 kV which it applies to a corona discharge conductor 3, by way of a connecting resistor R having a resistance of 10 ohms. The corona discharge conductor 3 has a pointed end and is spaced from a collector electrode 4, to define therewith an air gap. The collector electrode 4 is connected to ground via a further resistor R having a resistance of 10 ohms.

A transporting arrangement is provided for transporting sheets 8 along a predetermined path which passes through the air gap between electrodes 3 and 4. The transporting arrangement is comprised of two guide plates 6 and 7 defining a thin clearance along the length of which the sheets 8 can be passed. The sheets 8 themselves are moved along this path in direction of arrow A by transport rollers 9 and 10 which are driven by a non-illustrated drive motor.

In the region of the air gap between electrodes 3 and 4, the guide plates 6 and 7 are provided with openings 6a and 7a through which corona discharge current can flow from electrode 3 to collector electrode 4. The size of the openings 60 and 7a has been exaggerated in the drawing for the sake of clarity, and will advantageously be smaller. Also, it should be understood that the distance between the input end of the conveyor guide plates 6,7 and the drive rollers 8 and 9 is sufficiently small that the trailing edge of a sheet 8 inserted into the path defined by plates 6,7 will be engaged by nonillustrated transporting means located upstream of the input into conveyor 6, 7, 9, 10 at the moment when the leading edge of a sheet 8 is engaged by the transporting rollers 9 and 10. The non-illustrated upstream and downstream components of the sheet transporting arrangement have not been depicted, because they are not essential for an understanding of the invention. When there is no sheet 8 located in the region of the openings 6a and 7a, the corona discharge current can pass freely to the collector electrode 4.

The circuit junction 20 between electrode 4 and resistor. R is connected by way of conductor 11 to the input of an amplifier 12, which receives operating current via a supply line 13. The output of amplifier 12 is connected, via a further conductor 14, to a relay 15 the other terminal of which is connected to ground. The relay 15 controls a switch 17 which is connected by means of conductors 18 and 19 to an alarm unit and to a schematically depicted motor shutoff switch operative for terminating operation of transport rollers 9 and 10 when switch 17 becomes closed.

. The distance between the discharge spike 3 and the collector electrode 4 is so selected that, in the absence of a sheet 8 in the air gap therebetween, no voltage breakdown will occur. On the otherhand, the magnitude of the ionic current under such circumstances will be large enough to produce across resistor R a voltage drop sufficiently great to be detected by amplifier 12. When'a sheet 8 passing through the region of the openings 6a, 7a interrupts this ionic current, the voltage drop across resistor R falls markedly, so that substantially no input signal is applied to the amplifier 12. As a result. switch 17 becomes closed, causing an alarm signal to, be generated and causing the operation of transport rollers 9, 10 to become terminated. The alarm signal can be visual or acoustic. As a further possibility, the output of amplifier 12 can be connected to the input of a logiccircuit operative for triggering an alarm signal and/or terminating the sheet transporting operation when a sheet enters the detection zone out ofphase with the proper time of entry therefor. Alternatively, switch 17 could be-used to activate some functional group in a sheet-processing machine, such as an electrostatic copier, in response to detection of the arrival of a sheet in the detection zone 6a, 7a.

It has been found advantageous to employ an output voltage of +5 kV, and to employ a radius of curvature of 0.05 mm for the discharge spike or edge, with the length of the air gap between electrodes 3 and 4 being about l0 mm. The upper surface of rod-shaped collector electrode 4, which could also be of band-shaped configuration, should in such event be greater than about 12 mm*.

It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of circuits and constructions differing from the types described above.

While the invention has been illustrated and described as embodied in a method and apparatus for detecting sheet goods without physically contacting such goods, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gistof the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint ofprior art fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims:

1. In an arrangement for handling sheet goods, in combination, a corona discharge electrode having a pointed end; an elongated collector electrode spaced from said corona discharge electrode to form therewith an air gap; means for establishing a flow of ionic current across said air gap from said corona discharge electrode to said elongated collector electrode; transporting means for transporting sheet goods along a predetermined path passing through said air gap in direction transverse to the direction of elongation of said elongated collector electrode and so oriented that sheet goods travelling along said predetermined path and through said air gap do not physically contact said electrodes; and monitoring means operative for determining whether or not an article of sheet goods is located in said air gap by monitoring the magnitude of said ionic current.

2. The arrangement defined in claim 1, wherein said means for establishing a fiowof ionic current comprises means for establishing a predetermined potential difference across said electrodes, and wherein said'electrodes are spaced from each other a distance large enough to prevent developmentof a voltage breakdown across said air gap when no sheet goods are present in said air gap.

3. The arrangement defined in claim 2, wherein said means for establishing a predetermined potential difference comprises means for establishing acro'ss'said electrodes a potential difference of between 3 kV and 4. The arrangement as defined in claim 1, wherein said means for establishing a flow of ionic'current comprises means'for maintaining said corona discharge electrode at a potential of about 5 kV;

5. The arrangement defined in claim 4, wherein the radius of curvature of the discharge'end of said corona discharge electrode means is less than or equal to about 0.05 mm, and wherein the length of said air gap is between about 5 mm and about 12 mm.

'6. The arrangement defined in claim 1, and further including alarm means connected to said monitoring means and operative for issuing an alarm signal when the magnitude of said ionic current reaches a predetermined value.

7. The arrangement defined in claim 1, wherein said path is oriented perpendicular to the direction of elongation of said elongated collector electrode.

8. The arrangement defined in claim 1, wherein said elongated electrode is a rod-shaped electrode.

9. The arrangement defined in claim 7, wherein said elongated electrode is a rod-shaped electrode.

10. The arrangement defined in claim 1, wherein said path is oriented perpendicular to the direction of elongation of said elongated collector electrode and is so oriented that sheet goods travelling through said air gap pass along a plane parallel to said elongated collector electrode. 

1. In an arrangement for handling sheet goods, in combination, a corona dischArge electrode having a pointed end; an elongated collector electrode spaced from said corona discharge electrode to form therewith an air gap; means for establishing a flow of ionic current across said air gap from said corona discharge electrode to said elongated collector electrode; transporting means for transporting sheet goods along a predetermined path passing through said air gap in direction transverse to the direction of elongation of said elongated collector electrode and so oriented that sheet goods travelling along said predetermined path and through said air gap do not physically contact said electrodes; and monitoring means operative for determining whether or not an article of sheet goods is located in said air gap by monitoring the magnitude of said ionic current.
 2. The arrangement defined in claim 1, wherein said means for establishing a flow of ionic current comprises means for establishing a predetermined potential difference across said electrodes, and wherein said electrodes are spaced from each other a distance large enough to prevent development of a voltage breakdown across said air gap when no sheet goods are present in said air gap.
 3. The arrangement defined in claim 2, wherein said means for establishing a predetermined potential difference comprises means for establishing across said electrodes a potential difference of between 3 kV and 7 kV.
 4. The arrangement as defined in claim 1, wherein said means for establishing a flow of ionic current comprises means for maintaining said corona discharge electrode at a potential of about 5 kV.
 5. The arrangement defined in claim 4, wherein the radius of curvature of the discharge end of said corona discharge electrode means is less than or equal to about 0.05 mm, and wherein the length of said air gap is between about 5 mm and about 12 mm.
 6. The arrangement defined in claim 1, and further including alarm means connected to said monitoring means and operative for issuing an alarm signal when the magnitude of said ionic current reaches a predetermined value.
 7. The arrangement defined in claim 1, wherein said path is oriented perpendicular to the direction of elongation of said elongated collector electrode.
 8. The arrangement defined in claim 1, wherein said elongated electrode is a rod-shaped electrode.
 9. The arrangement defined in claim 7, wherein said elongated electrode is a rod-shaped electrode.
 10. The arrangement defined in claim 1, wherein said path is oriented perpendicular to the direction of elongation of said elongated collector electrode and is so oriented that sheet goods travelling through said air gap pass along a plane parallel to said elongated collector electrode. 